Hybrid automatic repeat request (HARQ) is a combination of forward error correcting coding and error detection utilizing an automatic repeat request error coding method. In general, a transmitter will send data to a receiver, and if the receiver can successfully decode the data then the receiver will send an acknowledgement (ACK) to the transmitter. Conversely, if the receiver cannot decode the data properly, the receiver will send a negative acknowledgement (NACK) to the transmitter.
Present retransmission mechanisms using HARQ techniques work by having an access point sending and resending one or more coded data blocks to the mobile device, which soft combines the transmissions to reconstruct the original data block. However, with increasing demand for higher data rates in many locations, it is expected that an increased number and variety of wireless access points that support higher data rates, but shorter range, will be deployed. As used in the present disclosure, an access point can be any point from which a mobile device can receive data, including, but not limited to, a cellular connection, a WiFi™ connection, a short-range connection among others.
The deployment of a high density of access points will result in an environment of dense and variable coverage of wireless access for mobile devices. While present retransmission mechanisms using HARQ may be suitable for environments where the mobile device can receive good quality signals from a single access point, such mechanisms may be poorly suited to dense, variable wireless coverage environments with overlapping coverage from multiple access points.